Lithium-ion batteries typically include an anode, an electrolyte, and a cathode that contains lithium in the form of a lithium-transition metal oxide. Examples of transition metal oxides that have been used as cathode materials include lithium cobalt dioxide, lithium nickel dioxide, and lithium manganese dioxide. None of these materials, however, exhibits an optimal combination of high initial capacity, high thermal stability, and good capacity retention after repeated charge-discharge cycling. Recently mixtures of transition metal oxides such as manganese, nickel, and cobalt oxides have been used as cathode materials for lithium-ion electrochemical cells.